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Topology Dissemination Based on Reverse-Path Forwarding (TBRPF)

Topology Dissemination Based on Reverse-Path Forwarding (TBRPF). <draft-ietf-manet-tbrpf-06.txt> Richard Ogier ogier@erg.sri.com September 21, 2002. Major Changes for Version 06. Section describing operation of TBRPF routing has been rewritten to improve readability.

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Topology Dissemination Based on Reverse-Path Forwarding (TBRPF)

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  1. Topology Dissemination Based on Reverse-Path Forwarding (TBRPF) <draft-ietf-manet-tbrpf-06.txt> Richard Ogier ogier@erg.sri.com September 21, 2002

  2. Major Changes for Version 06 • Section describing operation of TBRPF routing has been rewritten to improve readability. • HELLO messages have been modified to include relay priority. • New configurable parameter IMPLICIT_DELETION indicates whether link deletions are implied by link additions in topology updates. • Name has been changed by replacing “Broadcast” with “Dissemination”. Acronym is still TBRPF. • New IPR statement gives away all rights to all portions of TBRPF included in a jointly developed protocol (posted on the IETF page of IPR notices).

  3. Improved Description of TBRPF Routing • Organized with a separate subsection for each procedure (e.g., Processing Topology Updates). • Pseudocode format changed: Each procedure or algorithm is described using numbered steps in English, with less math notation. • Clarified that TBRPF computes the equivalent of multipoint relays (MPRs). • MPRs are used for topology dissemination and flooding of multiple interface and network prefix information. • Nodes select themselves as MPRs with respect to a subset of neighbors (in OLSR, an MPR is selected by neighbors of the MPR). • Neighbors in the reportable node set RN are equivalent to the MPR selectors of OLSR. • This equivalence makes it possible to merge TBRPF with OLSR. For example, MPRs can be selected as in OLSR while topology discovery is done as in TBRPF.

  4. Relay Priority • Each node advertises its relay priority in each HELLO. • A node with higher relay priority is more likely to: • Include more neighbors in RN • Report a larger part of its source tree • Be selected as a next hop relay. • A node with relay priority = 0 is equivalent to a non-relay node, which was already supported in previous versions of the draft. • Relay priority is similar to OLSR’s relay willingness (both teams independently decided to add this feature).

  5. Implicit Deletion Option • If IMPLICIT_DELETION = 1, then the addition of a link (u,v) in a Topology Update implies the deletion of any link (w,v) with the same head node. (Valid if the node reports only links in its source tree.) • Indicated by the “implicit deletion” bit in Topology Updates. • If a node uses the option of reporting redundant topology information (so that two links with the same head node can be reported), then IMPLICIT_DELETION must be 0, since in this case link deletion cannot be implied by link addition.

  6. New IPR statement for TBRPF • Grants a royalty-free license to everyone for any parts of TBRPF that either • become part of an IETF standard, or • are included in a jointly developed protocol, whether or not the protocol becomes a standard. • In addition, grants a royalty-free license for non-commercial (research) use of TBRPF while it is being evaluated by the IETF or is described in an Experimental RFC. • No need to apply for a license – automatic. • Posted on the IETF page of IPR notices. • May be modified based on feedback from the WG.

  7. Implementation Status • TBRPF has been implemented in Linux, ns-2, OPNET, and Qualnet. • Has been tested in networks of PDAs using Cisco and Lucent 802.11 cards. • Implementation is compliant with the latest draft, but does not include optional features.

  8. Rough plan for Experimental RFC • Review packet format, and possibly make minor changes to simplify it (e.g., exclude “simple mode” and always use 8 bits for message type). • Current version supports only 255 neighbors (8 bits). Possibly include an option bit that provides a 16-bit field for the number of neighbors. • HELLOs contain only neighbor RIDs (like OSPF). Possibly change this to neighbor interface IDs to handle special situations that can occur in wireless networks. • Possibly support multiple instances of TBRPF. • Possibly support authentication, either using a secret key and message digest as in OSPF, or using the IP Authentication Header [RFC 2402] proposed for IPSec. (This issue is common to all MANET protocols.) • Additional details may be needed to completely specify IPv6 operation. • Review draft for proper use of MUST, SHOULD, MAY, etc. • Other recommended changes, including style changes.

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